Salicylic acid influences Hsp70/Hsc70 expression in Lycopersicon esculentum: Dose- and time-dependent induction or potentiation

Overexpression of heat-shock (HS) proteins (HSP) is often sufficient to pro tect against lethal environmental stresses. Anti-inflammatory salicylates p otentiate the induction of the 70 kDa HSP (Hsp70) in mammals in response to HS and enhance thermotolerance. In plants, salicylic acid (SA) is a natura l signalling molecule, mediating resistance in response to avirulent pathog ens. The influence of SA on the HS response in plants is, however, unknown. We investigated the effect of SA, alone or with HS, on Hsp70/Hsc70 express ion in tomato cells using biometabolic labelling and Western blotting. A do se- and time-dependent influence on Hsp70/Hsc70 accumulation was observed: SA at 1.0 mM (3 h) potentiated heat-induced accumulation, while 1.0 mM (5 h ) and 0.5 mM (8 h) induced expression, the latter preceded by increased mem brane permeability. These results suggest that in plants, as in mammals, lo w SA concentrations do not induce Hsp70/Hsc70 expression but potentiate HS induction and confer membrane protection, while cytotoxic levels induce Hsp 70/Hsc70. (C) 1999 Academic Press.